Sequence diversity of two chloroplast genes: rps4 and tRNA Gly (UCC), in the liverwort Marchantia polymorpha, an emerging plant model system

The primary purpose of this study is to evaluate the sequence variation for two regions of chloroplast DNA in a collection of 27 taxonomically well-annotated clonal lines of Marchantia polymorpha sensu lato derived from European populations. We attempted to develop molecular markers so as to identify three taxa usually recognized as subspecies. We sequenced two regions: the rps4 gene along with the rps4-trnT intergenic spacer and an intron of the tRNAGly (UCC) gene. Samples of Marchantia paleacea ssp. diptera from Japan were used for comparative purposes. Three haplotypes (MA, MB, and MC) were identified for the species, and almost all sequence divergence between subspecies was found to occur at the level of 0.0023–0.0032 substitutions per site. The sequence divergence between M. polymorpha and M. paleacea was tenfold greater (0.0331–0.0340). We did not detect any differences between M. paleacea and homologous sequences from the reference chloroplast genome of M. polymorpha obtained from the GeneBank (NC_001319). It was confirmed that the cell suspension line A-18 used for the sequencing of the full chloroplast genome in 1986 was incorrectly taxonomically annotated.